1. Field of the Invention
The present invention relates to a motor and more specifically to a motor wherein the output thereof can be switched.
2. Description of the Related Art
An 8-pole, 10-slot and 20-segment DC motor with a wire winding devised for the down-sizing of the motor is known in the art (Japanese Patent Application Publication No. 2008-136343), although the output thereof cannot be switched. Specifically, magnetic poles are formed by 8 permanent magnets, and five-phase-coil structure are formed by allocating U, V, W, X, and Y phase respectively to the 10 slots of an armature. The 20 segments of a commutator are wound using connecting wires by an interval of 4 segments and are short-circuited.
A 4-pole, lap-winding motor where the rotational velocity can be switched is also known (Japanese Patent Application Publication No. 2006-353019). This motor is a multipolar motor having at least 4 poles and a winding structure by lap-winding, which includes a plurality of brushes arranged in equal intervals in the circumferential direction, and provides an operation mode of at least 2 speed types by selectively energizing the brushes. The plurality of brushes includes a positive electrode first brush and a positive electrode second brush disposed to oppose the positive electrode first brush, and a negative electrode first brush and a negative electrode second brush disposed to oppose the negative electrode first brush. This motor has a low speed mode where the positive electrode first brush and the negative electrode first brush are energized, and a high speed mode where all 4 brushes are energized.
Also, a multipolar motor having at least 4 poles and a lap-winding winding structure is known. This motor includes a first brush and a second brush used for a low speed operation, a third brush used with either the first or the second brush for a high speed operation, and an equalizer for connecting coils that need to have the same isoelectric potential among a plurality of coils. In this motor, brushes having the same electric potential can be removed, which thereby makes it possible to reduce the total number of brushes required.
Another known multipolar motor has a brush arranged in either a place moved by an advance-angle or by a delay-angle from the place opposing a first brush, a second brush, and a third brush in the rotating direction of a motor. According to this motor, a new operation mode can be realized without drastically increasing the number of brushes even in a multipolar device. For example, in this motor, when an equalizer is applied to a 6-pole device, a low speed mode can be operated with 2 brushes, although 6 brushes are normally required. At this point, 4 spaces become empty where the brushes are arranged normally, and these spaces can be used for arranging brushes for separate operation modes, which makes it possible to add 4 other kinds of operation modes other than the low speed mode and the high speed mode. That is, the more poles the motor has, the more it becomes possible to increase types of operation modes.
In general, when output switching is controlled by a multipolar motor having 8 or more poles, the configuration of a motor becomes complicated because the total number of brushes correspondingly increases. Accordingly, it is possible to reduce the number of brushes when coils having the same electric potential are connected with an equalizer as in the motor disclosed by Japanese Patent Application Publication No. 2006-353019. However, when an equalizer is connected, the number of required wire winding processes correspondingly increases, which deteriorates productivity.